General Information
In an elevator system, using a Relative System Response (RSR) measure to assign elevator cars to hall calls, the car to hall call travel time is expressed in terms of various time related penalties. These penalties are added together and summed with various penalties that penalize undesirable operating characteristics. Bonuses are given for desirable operating situations and these are subtracted from the sum of penalties resulting in the Relative System Response or RSR value. These values are calculated for each car for a given hall call and the car with the minimum RSR value is assigned to answer the hall call. The penalties and bonuses selected for various time delays and operating characteristics are either fixed or they are varied based on, for example, the past five (5) minute average hall call waiting time and the current hall call registration time.
The above schemes treat all hall calls equally without regard to the number of people waiting behind the hall call. They also treat all cars equally without regard to the current car load, unless the car is fully loaded. It considers only the current car load, but not the expected car load when the car reaches the hall call floor. As a result the car assigned in one cycle is often de-assigned later, because the car later becomes full, and another car is assigned. Often the assigned car does not have adequate capacity So, when it stops and picks up people, some people are left out, and they then need to re-register the hall call, resulting in increased waiting time and user irritation. An extra car has to be sent there, thus increasing the number of car stops and decreasing the system's handling capacity. When a large number of people are waiting, although more than one car will be needed to serve the waiting people, the prior RSR systems still assign only one car, resulting in delayed service and large waiting time for a large number of people.
When the cars stop at "en route" floors, the passenger transfer time depends on the number of people boarding and de-boarding the car. By using a fixed car stop penalty, the delays due to "en route" stops are only partially penalized. Large "en route" stops have a high probability of the cars being delayed, cars becoming full before reaching the hall call floor and cars making additional car call stops for car calls generated at "en route" hall call floors. These are detrimental to system performance, as they often cause hall call reassignment, but are not properly penalized.
Often heavily loaded cars are stopped for picking up one or two people. This increases the service time to a large number of people. The prior RSR systems do not distribute car load and car stops as effectively as possible, due to the lack of knowledge of the number of people waiting behind the hall calls and the number of people expected to be de-boarding and boarding the car at "en route" stops, and hence the expected car load when the car reaches the hall call floor.
For further general background information on RSR elevator car assignment systems, either with fixed or variable bonuses and penalties, reference is had to assignee's U.S. Pat. No. 4,363,381 issued to Joseph Bittar on Dec. 14, 1982, and the above-referenced Ser. No. 07/192,436, respectively. These approaches are further discussed below in the sub-section entitled "RSR Assignments of Prior Approaches."